In the case of eliminating or preventing vibration of a vibrating body such as an engine by using a vibration isolator, for example, an acceleration sensor is provided at an engine mount so as to control the vibration isolator based on a measured result of the acceleration sensor. In this case, if the acceleration sensor does not operate normally and properly, the vibration isolator cannot be controlled correctly and thus an effective elimination of vibration cannot be achieved. In order to avoid such issue, various acceleration sensor state detecting apparatuses have been considered for detecting whether the acceleration sensor operates properly.
JP07-174787A and JP11-190741A each disclose an acceleration sensor state detecting apparatus. According to the acceleration sensor state detecting apparatus disclosed in JP07-174787A, an upper limit value and a lower limit value are defined relative to a measured result of an acceleration sensor on the basis of a measured object thereof. When a state in which the measured result is above the upper limit value or below the lower limit value continues for a predetermined time or more, an error in the acceleration sensor is determined. In addition, according to the acceleration sensor state detecting apparatus disclosed in JP11-190741A, a rotation sensor for detecting a rotation speed of wheels is provided so as to detect a state of an acceleration sensor that measures an acceleration of a vehicle in motion. Then, an acceleration acquired on the basis of a measured result of the rotation sensor, and a measured result of the acceleration sensor are compared so as to detect an error in the acceleration sensor.
According to the acceleration sensor state detecting apparatus disclosed in JP07-174787A, the error in the acceleration sensor can be detected if the measured value thereof is retained over the upper limit value or below the lower limit value. However, an error that may possibly occur in the acceleration sensor when the measured value is specified between the upper limit value and the lower limit value cannot be detected. Further, according to the acceleration sensor state detecting apparatus disclosed in JP11-190741A, an error in the acceleration sensor occurring when the measured value thereof is retained between the upper limit value and the lower limit value can be detected. However, since the measured values by the other sensor and the acceleration sensor are compared for the detection of the error in the acceleration sensor, an error that might occur, in fact, in the other sensor may be mistakenly determined as the error in the acceleration sensor.
Thus, a need exists for an acceleration sensor state detecting apparatus that can accurately detect a state of an acceleration sensor.